1. Field of the Invention
The present invention relates to a cooling agent recovery technology and more particularly, to a cam wheel assembly for refrigerant recovery machine that is easy to fabricate and that utilizes wear strips to prolong the service life.
2. Description of the Related Art
A conventional refrigerant recovery machine utilizes a cam wheel assembly to move piston means, causing pump members to draw in a refrigerant from the main unit of a cooler system. FIG. 12 shows a cam wheel assembly for refrigerant recovery machine according to the prior art. According to this design, the cam wheel assembly a comprises a single-piece cam wheel a1, a sliding block a2 formed of two block members a21 and arranged around the cam wheel a1, a plurality of rolling needles a5 arranged in between the cam wheel a1 and the sliding block a2, rolling balls a4 mounted in a groove a22 on an outer side of each of the two block members a21 of the sliding block a2 and an open frame member a3 formed of two frame parts a31 and arranged around the sliding block a2. The open frame member a3 comprises two sliding grooves a32 bilaterally disposed on the inside corresponding to the grooves a22 of the sliding block a2. During rotation of the cam wheel a1, the sliding block a2 is forced to move the open frame member a3 transversely back and forth, causing reciprocation of pistons b. At the same time, the sliding block a2 moves up and down in the open frame member a3.
The aforesaid prior art cam wheel assembly a is capable of reciprocating the pistons b, however it still has numerous drawbacks as follows:
1. The open frame member a3 is formed of two frame parts a31. Due to complicated shape design, the frame parts a31 must be processed through a secondary processing process. Due to necessity of a secondary processing process, the frame parts a31 are made by means of powder metallurgy. However, because the frame parts a31 are made by means of powder metallurgy, they are less rigid. In consequence, the sliding grooves a32 wear quickly subject to friction by the rolling balls a4. If a rigid material is used to make frame parts a31 by forging, casting or other techniques, the cost will be relatively increased and the follow-up processing will be complicated.
2. Because the cam wheel a1 is a single-piece member, the two block members a21 of the sliding block a2 must be mounted around the single-piece cam wheel a1 and then fastened together with the rolling needles a5 set in between the cam wheel a1 and the sliding block a2 and the rolling balls a4 mounted in the grooves a22 of the sliding block a2 before installation of the open frame member a3. If the cam wheel assembly a starts to wear or is damaged, the user cannot use substitute component parts from the market for replacement and must ask the original machine provider to provide the necessary component parts for replacement.
3. The rolling balls a4 are mounted in the grooves a22 of the sliding block a2. During displacement of the sliding block a2, the rolling balls a4 in each groove a22 will be forced to hit one another, causing noises. Further, the rolling balls a4 tend to be gathered at one side in each groove a22, causing uneven loading on the sliding block a2 and quick wearing of the sliding block a2.